Polyester yarn and process for producing

ABSTRACT

A multi-filament poly(trimethylene terephthalate) yarn is provided. The poly(trimethylene terephthalate) yarn has a crystal orientation function of at least 0.6 and an elongation at break of between 65% and 110%. A process for producing the yarn is also provided in which poly(triemethylene terephthalate) is melt-spun into a multi-filament yarn, the yarn is cooled to a yarn temperature of less than 50° C., and the cooled yarn is taken-up at a take-up speed of at least 3500 m/min while maintaining the temperature of the yarn at a yarn temperature of less than 50° C.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser. No. 60/754,068 filed Dec. 27, 2005, the entire disclosure of which is herein incorporated by reference

FIELD OF THE INVENTION

The present invention relates to a polyester yarn. More particularly, the invention relates to a partially oriented poly(trimethylene terephthalate) yarn and a process for producing such yarn.

BACKGROUND OF THE INVENTION

Polyesters prepared by condensation polymerization of the reaction product of a diol with a dicarboxylic acid can be melt extruded and spun into a continuous multi-filament yarn suitable for use in textiles and carpets. After spinning, the yarn may be wound onto a package to form a partially oriented yarn package, or the yarn may be further processed immediately by heating and drawing the yarn to form a fully oriented yarn.

Fully oriented polyester yarns may be utilized directly in processes for forming textiles and carpets. Partially oriented polyester yarns, however, may be stored and/or shipped to a different location for further processing prior to use in textiles or carpets, such as by stretching and thermofixing the yarn or by stretch-texturing the yarn. Partially oriented yarns are preferred yarns for draw or stretch texturing because drawing, texturing, and heat setting operations can be carried out in an integrated manner, eliminating the need for expensive draw-twisting operations.

Continuous multi-filament poly(ethylene terephthalate) (PET) yarn, a commonly used polyester yarn, may be produced in multiple stages. Multi-filament PET partially-oriented yarns may be spun and wound onto a yarn package in a first stage, which, in a second stage, may be unwound from the yarn package and stretched into finished form and thermofixed or stretch-textured into bulky drawn-textured multi-filament yarns. Between these two stages, the packages of the multi-filament PET partially oriented yarns can be stored long-term and transported at elevated temperatures without any influence on the process conditions of the second texturing stage and the quality of the products.

Poly (trimethylene terephthalate) (PTT) is a recently commercialized polyester that has several characteristics desirable in textile and carpet applications, including high resiliency, soft hand, stain resistance, and low modulus. Unlike PET yarns, multi-filament PTT partially oriented yarn produced by conventional processes has presented many practical problems. One of the most serious problems is the instability of the partially oriented yarn. The instability of the yarn can be observed in various forms, including deformed yarn packages, change in the yarn properties as a function of time, and change in yarn properties as a function of depth of the yarn on the yarn package. These problems have limited the usefulness of multi-filament PTT partially oriented yarns.

In contrast to PET multi-filament partially oriented yarns, PTT multi-filament partially oriented yarns have a considerable shrinking tendency, both immediately after spinning and winding, as well as several hours or days after the yarn is wound onto a yarn package. The shrinking tendency of the PTT multi-filament partially oriented yarn causes the yarn to contract. The contracting yarn compresses the yarn package on which it is wound, sometimes to an extent that the yarn package can no longer be taken off the chuck. Further, during long-term storage or transport the yarn package does not maintain its desired shape, and forms bulges with hard edges that cause severe unwinding problems and extreme increase in uster values. Only limitation of the weight of the yarn packages to less than 2 kg provides a remedy for these problems, which typically do not occur during the processing of PET partially oriented yarns. Yarn packages of less than 2 kg, however, are less desirable than the commonly used 10 kg to 20 kg yarn packages since they are more difficult to store and ship and because, in subsequent use, they must be replaced far more often.

Furthermore, it has been observed that, relative to PET multi-filament partially oriented yarns, PTT multi-filament partially oriented yarns suffer age related defects to a larger extent during storage. A structural hardening of PTT partially oriented yarn occurs over time, changing the characteristics of the yarn (e.g. boil-off shrinkage and degree of crystallization) with time. Industrial use requires that multi-filament yarns maintain their characteristics with time so that subsequent processing of the yarns can be carried out continuously.

Partially oriented PTT multi-filament yarns produced according to conventional polyester spinning processes tend to have a high degree of shrinkage due to the relatively high degree of axial orientation induced in the yarns at conventional polyester take-up (spinning) speeds. The axial orientation induced in the amorphous phase of the multi-filament PTT polyester partially oriented yarn is lost due to entropy-driven disorganization of the amorphous phase as the yarn ages, resulting in shrinkage of the yarn. Comparatively, at typical commercial polyester spinning speeds of from 3000 m/min to 3200 m/min, little axial orientation is induced in PET yarn so the PET yarn does not shrink, and PET partially oriented yarn packages are shrink-stable.

As shown in U.S. Pat. No. 6,287,688, one approach used to eliminate the shrinkage problem of multi-filament partially oriented PTT yarns has been to reduce the take-up (spinning) speed used to spin the yarn to below 2600 m/min, for example from 1650 m/min to 2600 m/min or from 1000 m/min to 2000 m/min. Spinning at a low take-up speed produces a partially oriented PTT yarn that has a low degree of axial orientation in the amorphous phase and a low degree of crystallinity. The resulting yarn suffers less shrinkage problems than multi-filament PTT partially oriented yarns spun at conventional spinning speeds of from 3000 m/min to 3200 m/min since it has a relatively low degree of amorphous phase axial orientation that can be lost as a result of entropically-driven reorientation of the yarn. This process, however, produces a multi-filament PTT partially oriented yarn still subject to considerable shrinkage. The process is also not commercially viable due to the slow rate of yarn production at the required take-up speeds.

As shown in European Patent Application No. 1209262 A1, another approach used to eliminate the shrinkage problem of multi-filament PTT partially oriented yarns has been to heat the yarn to a temperature from 50° C. to 170° C. prior to winding the yarn on a yarn package. The heat treatment induces some crystallinity in the yarn, which reduces the shrinkage of the yarn after it is wound. The resulting yarn, however, lacks sufficient crystalline orientation to reduce shrinkage such that the shrinkage is truly negligible. The resulting partially oriented yarn may shrink up to 40% in a boiling water shrinkage test.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a yarn comprising a multi-filament poly(trimethylene terephthalate) yarn having a crystalline orientation function of at least 0.6 and an elongation at break of between 65% and 110%. In a preferred embodiment, the multi-filament poly(trimethylene terephthalate) yarn has a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage.

In another embodiment, the present invention is directed to a process for forming a shrink-stable partially oriented poly(trimethylene terephthalate) yarn comprising melt-spinning poly(trimethylene terephthalate); cooling the melt-spun poly(trimethylene terephthalate) into a multi-filament yarn having a yarn temperature less than 50° C.; and taking-up the multi-filament yarn having a yarn temperature less than 50° C. at a take-up speed of at least about 3500 m/min while maintaining the yarn at a yarn temperature of less than 50° C.

In still another embodiment, the present invention is directed to a yarn comprising, a poly(trimethylene terephthalate) yarn having an initial boil-off shrinkage of at most 22%; a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage; and an elongation at break of between 65% and 110%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an apparatus for spinning and winding a multifilament partially oriented yarn.

FIG. 2 is a schematic view showing a cross-section of a non-deformed cheese shaped yarn package.

FIG. 3 is a schematic view showing the cross-section of a yarn package not of the present invention in which bulging and shrinkage has occurred.

FIG. 4 is a graph showing the relation of crystal orientation function of a partially oriented PTT yarn to the spinning speed at which the yarn is spun.

FIG. 5. is a graph showing the relation of crystallinity of a partially oriented PTT yarn to the spinning speed at which the yarn is spun.

FIG. 6 is a graph showing the relation of the 30 day boil-off shrinkage of a partially oriented PTT yarn to the spinning speed at which the yarn is spun.

FIG. 7 is a graph showing the relation of birefringence of a partially oriented PTT yarn to the spinning speed at which the yarn is spun.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a partially oriented PTT multi-filament yarn subject to little or no shrinkage, and a process for producing such yarn. The partially oriented PTT multi-filament yarn of the present invention is particularly useful in the production of stable multi-filament PTT partially oriented yarn packages that may be stored or shipped to locations other than where the yarn was spun for further processing. In accordance with this invention, increasing the axial orientation of the multi-filament PTT partially oriented yarn beyond a certain point results in a highly oriented microfibrillar yarn structure that stabilizes the yarn against shrinkage instead of increasing yarn shrinkage. As shrinkage in multi-filament PTT partially oriented yarns is due to the rapidly induced axial orientation in spinning the yarn and subsequent relaxation of the induced orientation, it was unexpected that increasing axial orientation in a partially oriented PTT yarn would stabilize the yarn against shrinkage.

Further, while heating PTT multi-filament yarn above the cold crystallization temperature of the PTT yarn and subsequently drawing the heated PTT multi-filament yarn is known to significantly increase the crystallinity, orientation, and stability of a PTT yarn in the production of a fully oriented PTT multi-filament yarn, it was unexpected that increasing the orientation in a multi-filament PTT partially oriented yarn without inducing full orientation in the yarn and heat-setting the induced orientation would stabilize the yarn against shrinkage. Especially surprising was that increasing the axial orientation of partially oriented PTT multi-filament yarn without applying heat to the yarn above its cold crystallization temperature stabilized the yarn against shrinkage since it was expected that orientation would be increased in the amorphous phase without significantly increasing the crystallinity of the yarn. An increase in the orientation of the amorphous phase was expected to lead to a less shrink-stable partially oriented PTT multi-filament yarn since more of the yarn would be susceptible to relaxation of the orientation.

In the present invention the orientation of a PTT multi-filament partially oriented yarn may be increased by spinning the yarn and taking the spun yarn up at a take-up speed of at least 3500 m/min without thermosetting the yarn. The take-up speed of at least 3500 m/min places sufficient spin line stress on the yarn as it is spun to increase the orientation, and preferably crystallization, and most preferably the crystal orientation function of the yarn. Unexpectedly, the axial orientation induced in the PTT multi-filament partially oriented yarn of the present invention is relatively stable and the yarn is subject to little or no shrinkage.

The PTT multi-filament partially oriented yarn of the present invention has the additional advantage of being stronger than PTT multi-filament partially oriented yarns taken up at speeds lower than 3500 m/min, as measured by the yarn's tenacity. The tenacity of the PTT multi-filament partially oriented yarn of the present invention is preferably more than 2.5 grams/denier, more preferably at least 2.6 grams/denier, and most preferably at least 3.0 grams/denier.

DEFINITIONS

As used herein, the term “birefringence” is a measure of the total orientation of a fiber or a yarn, where the total orientation is a measure of the combined orientations of the crystalline phase and the amorphous phase of the fiber or yarn. Birefringence of PTT multi-filament partially oriented yarn is determined by measuring the amount of light retardation, F, caused by fiber anisotropy in PTT fiber under a cross-polar optical microscope using a rotating quartz compensator. When measuring F, the fiber sample is rotated 450 to the left or right of the extinction position to increase phase contrast. Three sets of measurements are taken and the average value is reported. The birefringence is calculated from the amount of light retardation and the fiber diameter, t, using the following equation: Birefringence=Γ/t

As used herein “boil-off shrinkage” is a measure of the degree of shrinkage of a yarn. Boil-off shrinkage may be measured according to the following procedure. A 4500 denier yarn skein is prepared using a standard denier creel with 1 m circumference. The 4500 denier yarn skein is prepared by measuring the denier of the yarn, calculating the number of times the yarn is required to be wrapped around the creel to provide a 4500 denier yarn skein according the to formula: # of wraps required=(4500/[measured yarn denier]); and wrapping the yarn around the creel the calculated # of wraps. The initial skein length (L_(i)) is measured by hanging a 500 g load on the skein and measuring the length of the skein. The skein is then folded and covered with gauze to prevent entanglement. The folded skein is then put in a boiling water bath for 30 minutes, after which it is taken from the bath and allowed to cool for 15 minutes. The skein is then padded dry with a cloth, and the length of the skein after shrinkage (L_(s)) is measured by hanging a 500 g load on the skein and measuring the length of the skein. The boil-off shrinkage (%) is determined according to the following formula: Boil-off shrinkage (%)=[(L _(i) L _(s))/L _(i)]*100

As used herein, “crystalline/amorphous lamellar period” is defined as the average length of the crystalline and amorphous lamellae arranged vertically in the microfibrillar structure measured by small-angle X-ray scattering.

As used herein, the term “crystalline orientation” is defined as the degree of axial orientation induced in a yarn or a filament by the crystalline phase of the yarn or filament. The crystalline orientation includes the degree of orientation in the yarn or filament of the crystalline portion of the yarn or filament. The crystalline orientation also includes the degree of orientation the crystalline phase of the yarn or filament may induce in the amorphous phase of the yarn or filament by holding the amorphous phase in an orientation within the yarn or filament by, for example, entanglement, bonding, or constriction. The crystalline orientation is a measure of the degree of orientation within the yarn or filament that is not susceptible to significant relaxation. Comparatively, birefringence is a measure of the total orientation of the crystalline and amorphous phases of a yarn or filament, including orientation in the amorphous phase that is susceptible to significant relaxation and that is not held in an orientation within the yarn by the crystalline phase.

As used herein, the term “crystal orientation function” is defined as a measure of the crystalline orientation of a yarn or filament. The crystal orientation function, f_(c), is measured using a wide-angle X-ray diffractometer on the yarn or filament from the azimuthal scan of the (010) reflection intensity, I(α), at 15.66°2θ angle. The scanned azimuthal angle, α, is from 0 to 90°. The crystal orientation function f_(c) may then be calculated using the following equations:

Sine squared average angle, <sin² α>, of yarn/filament (010) reflection made with the draw direction: $< {\sin^{2}\alpha_{010}}>=\frac{\int_{0}^{\pi/2}{{I(\alpha)}\sin^{3}\alpha_{010}{\mathbb{d}\alpha}}}{\int_{0}^{\pi/2}{{I(\alpha)}\sin\quad\alpha_{010}{\mathbb{d}\alpha}}}$

Orientation of (010) reflection, f₀₁₀ is given by: $f_{010} = {{1 - \frac{3}{2}} < {\sin^{2}\alpha_{010}} >}$

Since (010) is an equatorial reflection, it is related to the orientation of yarn/filament fiber axis, the crystal orientation function, by f _(c)=−2f ₀₁₀

As used herein, the term “crystallinity” is a measure of the degree (or fraction, as %) of crystallization of a yarn. Crystallinity may be determined using a differential scanning calorimeter (DSC), for example, a Perkin-Elmer DSC-7. A sample of yarn is placed in an aluminum pan and is heated from 30° C. to 270° C. at a rate of 10° C. per minute. The heat of fusion (ΔH) of the melting endotherm is measured with the DSC at about 228° C. if the PTT polymer is a homopolymer with no added polymers, and from about 215° C. to about 228° C. if the PTT polymer contains comonomers or other polymers. If the DSC scan shows any low temperature cold crystallization or pre-melting exotherms, as shown by an absorption at from about 70° C. to about 150° C., the measured heat of fusion may be corrected by subtracting the measured exotherms from the heat of fusion to give the corrected heat of fusion (ΔH_(corrected)). If no low temperature exotherms are shown by the DSC scan then, for the purposes of the equation below, ΔH_(corrected) will equal the measured ΔH at about 215° C. to 228° C. The crystallinity (%) of the sample may be calculated according to the following equation: Crystallinity (%)=(ΔH _(corrected) /ΔH _(f))*100 where ΔH_(f) is the heat of fusion of 100% crystalline PTT, which is defined as 35 cal/g.

Alternatively, the heat of fusion AH may be measured by heating the yarn to a temperature above its melting point, preferably to a temperature of from 245° C. to 255° C. until the yarn is completely melted, cooling the melted yarn to a temperature of from about 160° C. to 180° C., and then reheating the cooled melted yarn to a temperature of 270° C. at a rate of 10° C. per minute. Upon reheating through the melting point, the heat of fusion (ΔH) is measured with the DSC at about 228° C. if the PTT polymer is a homopolymer with no additional polymers, or from about 215° C. to about 228° C. if the PTT polymer contains other comonomers or other polymers. No correction is required for low temperature cold crystallization exotherms as heating the yarn above the melting point initially before measuring the heat of fusion exotherm eliminates crystallinity that causes the low temperature exotherms. The percent crystallinity may be determined according to the above equation where ΔH_(corrected) is equal to ΔH.

The degree of crystallinity of the yarn is also related to the density of the yarn. Specifically, the percentage of the yarn that is crystalline can be determined from the measured density according to the following equation: % crystallinity=Dc/Dm×[(Dm−Da)/(Dc−Da)]×100%, where Dm is the measured density, Dc is the density of 100% crystalline yarn, and Da is the density of 100% amorphous yarn (0% crystallinity). Dc=1.442 and Da=1.295 for PTT yarns. The measured density Dm may be determined in a density/gradient column at a temperature of 23±0.1° C. Sodium bromides of two concentrations may be used to bracket the expected density of the materials to be tested.

As used herein, the term “elongation at break” is defined as the increase in length of a yarn caused by a tensile force from a relaxed state to yarn breakage, measured as a percent increase in length of the yarn at its breaking point over the length of the relaxed yarn at full extension. The elongation at break may be measured in a Statimat tensile tester according to American Standard Testing and Materials (ASTM) Method D2101. An average of ten tests is reported.

As used herein, the term “heat of fusion” of a PTT yarn is defined as the amount of heat required to convert a unit mass of PTT yarn from its solid state at the melting point of PTT to its liquid state without an increase in temperature. The heat of fusion of PTT yarn may be determined using a differential scanning calorimeter (DSC) as described above.

As used herein, the term “initial”, when used in describing a characteristic or a measurement of a yarn or filament, is defined as the characteristic or measurement of the yarn or filament as determined within 24 hours of the yarn being spun. For example, the initial boil-off shrinkage of a yarn is the boil-off shrinkage of the yarn as determined within 24 hours of the yarn being spun.

As used herein, the term “melt-spinning” a polymer is defined as a process in which a polymer is melted by heating the polymer to or above its melting point, and extruding the melted polymer through one or more spinnerets.

As used herein, the term “partially oriented yarn” is defined as a polymer filament yarn that has moderate to high extensibility, preferably having an elongation at break of greater than 65% , which is indicative of lesser crystallinity than a fully oriented yarn, typically less than 45-50% crystallinity. A partially oriented yarn is typically a yarn that has not been heated to above its glass transition temperature or its cold crystallization temperature and then been drawn while heated.

“Partially oriented PTT yarn” or “PTT partially oriented yarn” as used herein is defined as a yarn formed of PTT polymer having an elongation at break of 65% or greater as measured in accordance with ASTM Method D2101.

“PET” as used herein means poly (ethylene terephthalate).

“PTT” as used herein means poly (trimethylene terephthalate).

“PTT polymer”, as used herein, is defined as a polyester polymer that contains at least 85 wt. % PTT and up to 15 wt. % comonomer; other polymer, including PET, polybutylene terephthalate, and nylon; additives such as catalysts, stabilizers, anti-static agents, antioxidants, flame retarding agents, colorants, colorant absorption modifiers, light stabilizers, organic phosphites, optical brighteners, and matting agents; or a mixture thereof.

“PTT yarn”, as used herein, is defined as a polyester yarn which contains at least 85 wt. % PTT and up to 15 wt. % comonomer or other polymer.

As used herein, the terms “shrink-stable” and “subject to little or no shrinkage” in reference to a yarn or a filament is defined to mean that the yarn or filament has an initial boil-off shrinkage of at most 22% and has a boil-off shrinkage after 30 days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage.

As used herein, the term “take-up speed” is defined as the speed of the take-up mechanism that takes up the yarn from the spinneret. The take-up mechanism is preferably a roll or set of rolls, and most preferably is godet rolls, however, it may be any spinning take-up mechanism conventional in the art of spinning yarn.

As used herein, the term “tenacity” is a measure of the strength of a yarn. Tenacity may be measured by using a Statimat yarn tensile tester according to ASTM Method D2101. An average of ten tests is reported.

Process of Producing a Shrink-Stable Partially Oriented PTT Yarn

A PTT multi-filament partially oriented yarn subject to little or no shrinkage in accordance with the present invention may be produced by melt-spinning poly(trimethylene terephthalate), cooling the melt-spun PTT into a multi-filament yarn having a yarn temperature of less than 50° C., and taking up the multi-filament yarn at a take-up speed of at least about 3500 m/min while maintaining the yarn at a temperature of less than 50° C. Taking-up the spun yarn at a speed of at least 3500 m/min generates sufficient spin line stress on the yarn as it is spun to induce sufficient orientation and crystallinity in the yarn to stabilize the yarn against shrinkage.

To produce the PTT multi-filament partially oriented yarn of the invention, PTT polymer is provided for melt extrusion. PTT polymers are known in the art, as are methods for making PTT polymers. PTT polymer can be obtained by the polycondensation reaction of terephthalic acid with equimolar quantities of 1,3-propanediol. The PTT polymer may be a homopolymer, or may be a PTT co-polymer containing minor amounts of non-PTT co-monomers. Suitable examples of PTT co-polymers include those that contain, in addition to repeating PTT monomer units, at most 15 mol %, preferably at most 10 mol %, and more preferably at most 5 mol % of co-monomers. Such co-monomers may include, but are not limited to, ethylene glycol, 1,4-cyclohexanedimethanol, oxalic acid, succinic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodiumsulfoisophthalic acid, isophthalic acid, and/ or adipic acid. In the present invention, however, use of a PTT homopolymer is preferred.

The PTT polymer may also be blended with minor amounts of other polymers such that the other polymers do not exceed 15 wt %, preferably 10 wt. %, and more preferably 5 wt. % of the PTT polymer blend. The PTT polymer may be blended with other polymers by melting the PTT polymer and other polymer or polymers together, or by melting the PTT polymer and other polymer or polymers separately and combining the melted polymers. Other polymers useful for blending with the PTT polymer in the process of the present invention include PET, poly (butylene terephthalate), and nylon.

The PTT polymer may contain small quantities of additional additives as admixtures. Such additives include catalysts, stabilizers, anti-static agents, antioxidants, flame retarding agents, colorants, colorant absorption modifiers, light stabilizers, organic phosphites, optical brighteners, and matting agents. The PTT polymer preferably contains from 0 to 5 wt. % of such additives in relation to the total weight of the PTT polymer.

PTT polymers having an intrinsic viscosity of from 0.7 dl/g to 1.3 dl/g are particularly useful in the process of the present invention. Most preferably PTT polymers having an intrinsic viscosity of from 0.85 dl/g to 1.1 dl/g are used in the process of the present invention.

Referring now to FIG. 1, PTT polymer chips or pellets may be melted and extruded through a spinneret 1 to form filaments 2 (i.e. the PTT polymer is melt-spun to form filaments 2). Preferably the PTT polymer chips or pellets are dried in advance of extrusion to a water content of at most 30 ppm, and more preferably to a water content of at most 15 ppm to minimize degradation of the PTT polymer. The PTT polymer may be melted and extruded in a conventional single-screw or twin-screw thermoplastic extruder having the spinneret 1 attached to the outlet of the extruder.

The PTT polymer may be heated in the extruder, or prior to entering the extruder, to a temperature at which the PTT polymer melts or higher but below a temperature at which the PTT polymer undergoes significant degradation. The melt temperature of homopolymer PTT is from about 225° C. to about 240° C., and the melt temperature of PTT polymer containing co-monomers or co-polymers may range from 200° C. to 250° C. Preferably, the PTT polymer may be heated to a temperature of at least 245° C. to melt the polymer. Also, preferably, the PTT polymer may be heated to a temperature below a temperature at which the PTT polymer undergoes significant degradation. Preferably the PTT polymer may be heated to a temperature of at most 280° C. Most preferably the PTT polymer may be heated to a temperature of from 250° C. to 260°. The extruder may be a multi-stage extruder wherein the PTT polymer is heated at different temperatures within the stages of the extruder. For example, the extruder may be four stage extruder in which the PTT polymer is heated to 245° C. to 250° C. in the first stage, from 250° C. to 255° C. in the second stage, and from 255° C. to 260° C. in the third and fourth stages.

The molten PTT polymer may be extruded through the spinneret 1 to form a plurality of melt-spun continuous filaments 2 exiting the spinneret 1 through multiple die holes in the spinneret die face 4. The die holes in the spinneret die face 4 preferably have a round cross-section, however, the die holes may have other shapes such as trilobal, delta, and other non-round cross-sections typically used in the partially oriented yarn industry. The die holes may have a size selected to provide desired characteristics to the yarn. Preferably the die holes have a diameter of from 0.1 to 0.5 mm, more preferably from 0.2 to 0.4 mm. The spinneret 1 preferably has sufficient die holes to provide a sufficient number of filaments 2 to form into a yarn of desired characteristics. For example, the spinneret 1 preferably may have from 10 to 100 die holes through which the molten PTT may be extruded into filaments 2. Multiple spinnerets (not shown) may be coupled to the extruder to enable multiple yarns to be spun simultaneously from the molten PTT polymer.

The melt-spun PTT polymer is cooled to form a multi-filament yarn having a yarn temperature less than 50° C. Preferably, melt-spun filaments 2 are cooled by quench air while being combined to form the multi-filament yarn 7.

In a preferred embodiment, the filaments 2 initially exit the spinneret 1 into a delay quench zone 3 located between the die face 4 of the spinneret and quench air 5. The delay quench zone 3 provides a zone in which the molten filaments may equilibrate prior to being subjected to cooling quench air, inhibiting the development of irregularities such as uneven thickness or uneven elongation. The delay quench zone 3 may have a length of from 0.1-30 centimeters, preferably from 0.5-20 centimeters. The delay quench zone 3 is preferably heated to 265° C. In an alternative embodiment, there is no delay quench zone 3.

The filaments 2 may then be cooled and solidified into a multi-filament yarn. After passing through the delay quench zone 3 (if there is a delay quench zone), the filaments 2 may be cooled by exposing the filaments 2 to quench air 5 in a quench air zone, where the quench air zone may have a length of from 0.1 to 2 meters. The quench air 5 preferably has a cold temperature relative to the temperature of the filaments exiting the delay quench zone 3 or spinneret 1. Most preferably the quench air temperature is from 10° C. to 30° C. If no delay quench zone 3 is utilized, the quench air temperature is preferably at the low end of the temperature range above, preferably from 10° C. to 20° C. The quench air 5 is preferably blown across the filaments 2, or optionally may be blown along the length of the filaments 2. Preferably the quench air 5 is blown at a velocity of from 0.1 to 0.8 m/sec, more preferably from 0.3 to 0.7 m/sec. Most preferably, the quench air 5 has a humidity of from 50% to 98%, more preferably 65 to 85%.

In one embodiment, amongst others, the filaments 2 pass through a quench air box or cylinder (not shown) surrounding the filaments 2 which defines the air quench zone in which the filaments 2 are exposed to the quench air 5. The quench air 5 may be directed inward from the interior surface of the quench air box or cylinder to cool the filaments 2.

The filaments 2 may be converged while being cooled with the quench air 5 into a multi-filament yarn 7. The resulting multi-filament yarn 7 may be also be cooled by the quench air 5. In another embodiment, the melt-spun filaments may be combined into a multi-filament yarn prior to cooling with quench air, where the resulting multi-filament yarn is cooled with the quench air. In yet another embodiment, the filaments may be combined to form a multi-filament yarn after the filaments have been treated with quench air. In each embodiment, however, the resulting multi-filament PTT yarn has a yarn temperature of less than 50° C. prior to being taken-up by the take-up mechanism.

The multi-filament PTT yarn 7 may be passed through a spin finish applicator 6, shown in FIG. 1 as an oiling roll, to apply a finishing agent on the yarn 7. The finishing agent is preferably an oil agent containing a fatty acid ester and/or mineral oil, or a polyether.

The multi-filament PTT yarn 7 is then taken-up by a take-up mechanism at a take-up speed of at least 3500 meters per minute (m/min), or at least 3600 m/min, or at least 3700 m/min, or at least 3800 m/min, or at least 3900 m/min, or more preferably at least 4000 m/min, to impart spin line stress in the yarn 7 as it is spun, thereby inducing a significant degree of axial orientation in the yarn 7. Preferably the yarn 7 is taken-up at a take-up speed of at most 5400 m/min, or at most 5300 m/min, or at most 5200 m/min, or at most 5100 m/min, or at most 5000 m/min. Preferably, the yarn 7 is taken-up at a take-up speed of from 3500 m/min to 5400 m/min, more preferably from 3800 m/min to 5000 m/minute, and most preferably from 4000 m/min to 4500 m/min.

The multi-filament PTT yarn may be taken-up by a take-up mechanism operating at the desired take-up speed. The take-up mechanism may be any conventional mechanism for taking-up a multi-filament yarn. The multi-filament PTT yarn 7 is preferably taken up by godet rolls 8 rotating at the desired take-up speed.

The multi-filament PTT yarn 7 is taken-up at the desired take-up speed, which must be at least 3500 m/min, while the yarn is maintained at a yarn temperature of less than 50° C. If godet rolls 8 are used to take-up the yarn, the godet rolls 8 are preferably unheated or cooled below ambient temperature, but, if heated, have a temperature that heats the yarn to a temperature less than the cold crystallization temperature of the yarn 7. Most preferably, the godet rolls 8 are unheated, but, if heated, the godet rolls 8 have a temperature that heats the yarn to a yarn temperature of less than 50° C.

If desired, other sets of godet rolls may be positioned between the take-up mechanism and the winder to smooth the take-up and winding process. The other sets of godet rolls should not operate at a speed effective to impart substantial draw to the yarn. Preferably, the other sets of godet rolls should be free rotating rolls or should be driven at a speed equal to the take-up speed or slightly less than the take-up speed, preferably 0% to 5% below the take-up speed, more preferably 0% to 1% below the take-up speed.

The resulting partially oriented PTT multi-filament yarn 7 may then be wound about a yarn package 9 at a winding speed preferably from 0% to 5% below the take-up speed of the take-up mechanism (e.g. godet rolls 8), and more preferably from 0% to 1% below the take-up speed. Winding the yarn 7 at a rate slightly below the take-up speed may reduce the stress on the yarn 7 as it is wound onto the yarn package 9.

The yarn package may be any conventional yarn package such as a cheese-shaped yarn package 11 shown in FIG. 2. Importantly, the PTT multi-filament partially oriented yarn may be wound onto a yarn package of a size such that the yarn 7 and yarn package 11 weigh at least 5 kg, 10 kg, or 15 kg. The resulting yarn package 11 is preferably stable against yarn shrinkage induced deformation since the yarn is subject to little or no shrinkage. For comparative purposes, FIG. 3 shows a yarn package 15 having a yarn 13 (not of the present invention) thereon where the yarn 13 has induced deformation in the yarn package 15.

The yarn package 11 may be used subsequently in further processes such as draw or stretch texturing operations. The PTT multi-filament partially oriented yarn 7 wound on the yarn package 11 may be unwound from the yarn package 11, and, upon being unwound may be subjected to drawing and texturing operations. The yarn package 11 may be stored for a period-for example, at least one day, at least one week, or at least 30 days-prior to use in further processes such as drawing and texturing. The stored yarn package 11 is preferably stable against yarn shrinkage induced deformation during storage and subsequent use. Alternatively, the yarn package 11 may be transported from the location at which the yarn 7 is wound onto the yarn package 11 for use in further processes at a different location. The transported yarn package 11 is preferably stable against yarn shrinkage induced deformation during transportation and subsequent use. The high take-up speed of at least 3500 m/min at which the PTT partially oriented yarn of the invention is spun preferably generates sufficient spin line stress in the yarn as it is spun to induce a crystal orientation function in the yarn of at least 0.6, more preferably at least 0.7, more preferably at least 0.8, and most preferably at least 0.9. As shown in FIG. 4, there are three distinct regions of crystal orientation function in PTT partially oriented yarns as a function of take-up speed. At low take-up speeds of 2900 to 2500 m/min or below the PTT partially oriented yarns have a low crystal orientation function reflecting that little stable orientation has been induced in the yarns by spin line stress. At conventional polyester take-up speeds of from 3000 m/min to 3200 m/min, and up to 3500 m/min, the PTT partially oriented yarns have rapidly increasing crystal orientation function reflecting increasing stable orientation induced in the yarns by spin line stress, but insufficient stable orientation for the yarn to be shrink-stable. At the high take-up speeds provided in the present invention of at least 3500 m/min, the PTT partially oriented yarns have a high crystal orientation function. Without wishing to be bound by theory, it is believed that partially oriented yarns spun at a take-up rate of at least 3500 m/min are shrink-stable without thermosetting, at least in part, because sufficient crystalline orientation has been induced in the yarn by spin line stress that the yarn is relatively stable against relaxation.

The high take-up speed of at least 3500 m/min at which the PTT partially oriented yarn of the present invention is spun may generate sufficient spin line stress in the yarn as it is spun to induce a crystallinity of at least 35% (corresponding to a density of at least 1.344 g/cm³), more preferably at least 36% (corresponding to a density of at least 1.345 g/cm³), more preferably at least 37% (corresponding to a density of at least 1.347 g/cm³), more preferably at least 38% (corresponding to a density of at least 1.348 g/cm³), more preferably at least 39% (corresponding to a density of at least 1.350 g/cm³), and most preferably at least 40% (corresponding to a density of at least 1.351 g/cm³) . As shown in FIG. 5, the crystallinity of PTT partially oriented yarn increases at higher take-up speeds, and at the high take-up speeds of at least 3500 m/min provided in the present invention the PTT partially oriented yarns have a relatively high degree of crystallinity compared to other PTT partially oriented yarns spun at lower take-up speeds, such as those used in conventional polyester spinning of 3000 m/min to 3200 m/min, and particularly those used at low take-up speeds below 2600 m/min. Without wishing to be bound by theory, it is believed that these yarns spun at take-up speeds of at least 3500 m/min are shrink-stable without thermosetting, at least in part, because sufficient crystallinity has been induced in the yarn by spin line stress that the yarn is stable against relaxation.

The high take-up speed of at least 3500 m/min at which the PTT partially oriented yarn of the invention is spun also may generate sufficient spin line stress in the yarn as it is spun to induce an initial boil-off shrinkage of at most 22%, more preferably at most 20%, more preferably at most 19%, more preferably at most 18%, and most preferably at most 17%. Without wishing to be bound by theory, it is believed that the decrease in initial boil-off shrinkage correlates to the increase in crystalline orientation, as shown by the increase in crystal orientation function in FIG. 4.

The high take-up speed of at least 3500 m/min at which the PTT partially oriented yarn of the present invention is spun may also generate sufficient spin line stress in the yarn as it is spun to induce a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage, more preferably from the initial boil-off shrinkage less 8% to the initial boil-off shrinkage, more preferably from the initial boil-off shrinkage less 6% to the initial boil-off shrinkage, and most preferably from the initial boil-off shrinkage less 5% to the initial boil-off shrinkage. For example, if the initial boil-off shrinkage of a PTT partially oriented yarn produced according to the process of the present invention is 17%, then the boil-off shrinkage after thirty days is preferably from 7% to 17%, more preferably from 9% to 17%, more preferably from 11% to 17%, and most preferably from 12% to 17%. As shown in FIG. 6, the thirty day boil-off shrinkage of PTT partially oriented yarn decreases markedly as the take-up speed at which the yarn is spun approaches 3500 m/min, and is maintained at a low level at take-up speeds of 3500 m/min and higher.

The high take-up speed of at least 3500 m/min at which the PTT partially oriented yarn of the invention is spun may also generate sufficient spin line stress in the yarn as it is spun to induce an initial birefringence in the yarn of at least 0.05. More preferably the high take-up speed of at least 3500 m/min at which the PTT yarn is spun induces an initial birefringence of from 0.06 to 0.085. As shown in FIG. 7, the birefringence of PTT partially oriented yarn increases as the take-up speed at which the yarn is spun increases.

The high take-up speed of at least 3500 m/min at which the PTT yarn is spun also preferably generates sufficient spin line stress in the yarn as it is spun to induce in the yarn: a microfibrillar structure which shows a two-point meridianal small-angle X-ray scattering with a crystalline/amorphous phase lamellar periodicity of from about 50 to about 100 angstroms in contrast to a four-point diagonal small-angle X-ray scattering of PET fiber (i.e. the PTT yarn of the present invention's lamellar periodicity is arranged in layers along the fiber direction instead of being staggered diagonally as in PET fiber); a tenacity of at least 2.5 grams/denier, more preferably at least 2.6 grams/denier, more preferably at least 2.7 grams/denier and most preferably at least 3.0 grams/denier; an elongation at break between 70% and 110%, more preferably from 75% to 105%; and a heat of fusion of at least 12 calories/gram (50.2 J/g), more preferably at least 13 cal/g (54.4 J/g), more preferably at least 14 cal/g (58.6 J/g), and most preferably at least 15 cal/g (62.8 J/g).

PTT Partially Oriented Yarn Composition

The present invention is also directed to a multi-filament PTT partially oriented yarn subject to relatively little shrinkage. The multi-filament PTT partially oriented yarn of the present invention may have a crystal orientation function of at least 0.6, more preferably at least 0.7, more preferably at least 0.8, and most preferably at least 0.9. The multi-filament PTT partially oriented yarn of the present invention may have a heat of fusion of at least 12 cal/g (50.2 J/g), more preferably at least 13 cal/g (54.4 J/g), more preferably at least 14 cal/g (58.6 J/g), and most preferably at least 15 cal/g (62.8 J/g) corresponding to a crystallinity of at least 35% (a density of at least 1.344 g/cm³), more preferably at least 36% (a density of at least 1.345 g/cm³), more preferably at least 37% (a density of at least 1.347 g/cm³), more preferably at least 38% (a density of at least 1.348 g/cm³), more preferably at least 39% (a density of at least 1.350 g/cm³), and most preferably at least 40% (a density of at least 1.351 g/cm³). The multi-filament PTT partially oriented yarn of the invention may have an initial boil-off shrinkage of at most 22%, more preferably at most 20%, more preferably at most 19%, more preferably at most 18%, and most preferably at most 17%. The multi-filament PTT partially oriented yarn of the invention may have a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage, more preferably from the initial boil-off shrinkage less 8% to the initial boil-off shrinkage, more preferably from the initial boil-off shrinkage less 6% to the initial boil-off shrinkage, and most preferably from the initial boil-off shrinkage less 5% to the initial boil-off shrinkage. The multi-filament PTT partially oriented yarn of the invention also may have an initial birefringence of at least 0.05, and most preferably an initial birefringence of from 0.06 to 0.085. The multi-filament PTT partially oriented yarn of the invention also may have a microfibrillar structure which shows a two-point meridianal small-angle X-ray scattering with a crystalline/amorphous phase lamellar periodicity of from about 50 to about 100 angstroms; a tenacity of at least 2.5 grams/denier, more preferably at least 2.6 grams/denier, more preferably at least 2.7 grams/denier, and most preferably at least 3.0 grams/denier; and an elongation at break of greater than 65%, greater than 70%, at least 75%, less than 110%, at most 105%, at most 100%, between 65% and 110%, between 70% to 105%, or from 75% to 100%.

As shown in FIG. 2, the multi-filament PTT partially oriented yarn of the invention 7 is preferably wound about a yarn package, for example a cheese-shaped yarn package 11. The yarn package 11 may be any conventional yarn package, and preferably is a yarn package of a size and dimension such that the yarn and yarn package weigh at least 5 kg, 10 kg, or 15 kg.

The yarn package 11 with the PTT partially oriented yarn of the invention 7 wound thereabout is more stable against yarn shrinkage induced deformation than conventional PTT partially oriented yarns. Shrinkage and deformation of the yarn package 11 preferably does not occur. If shrinkage occurs, however, it does not occur to such an extent that the yarn package 11 is deformed—forming bulges with hard edges—and cannot be taken off the chuck, as schematically illustrated in FIG. 3 (which illustrates a shrink-unstable PTT partially oriented yarn 13 not of the present invention wound on a yarn package 15 deformed by shrinkage of the unstable yarn 13).

EXAMPLE 1

Partially oriented PTT multi-filament yarns were prepared in accordance with the process of the present invention at take-up speeds of 3500 m/min, 4000 m/min, and 4500 m/min and measured for crystallinity, birefringence, crystal orientation function, and heat of fusion. PTT polymer having an intrinsic viscosity of 0.92 dl/g was dried at 130° C. with a hot air dryer for 6 hours to a moisture content of less than 30 ppm. The hot air had a dew point of less than -60° C. The dried polymer was melted and extruded using a 30:1 L/D 1-inch single screw extruder at 260° C. with a 50 hole spinneret. The extruded fibers were quenched with quench air having a temperature of 16° C. to a yarn temperature less than 50° C., passed through a pair of unheated godet rolls in the form of an S-wrap, and wound up with a Barmag SW 46SSD winder to produce a 150 denier yarn. One yarn was spun with the godet rolls taking-up the yarn at a take-up speed 3500 m/min, another was spun at a take-up speed of 4000 m/min, and a third was spun at a take-up speed 4500 m/min. The crystallinity, birefringence, crystal function, and heat of fusion of each yarn were measured. The resulting measurements are reported in Table 1 below. TABLE 1 Take-up Crystal Speed Heat of Fusion Crystallinity orientation (m/min) cal/g (%) Birefringence function 3500 13.1 37.5 0.068 0.93 4000 14.3 40.9 0.074 0.95 4500 15.3 43.8 0.080 0.95

The measured crystallinity, birefringence, crystal function, and heat of fusion for the yarns as shown in Table 1, indicate that the partially oriented PTT yarns spun at take-up speeds of 3500 m/min or higher and a yarn temperature less than 50° C. have a significant degree of orientation.

EXAMPLE 2

The boil-off shrinkage after thirty days of the yarns prepared in Example 1 was measured to determine the shrink capacity of the yarns after aging. The yarns were wound and stored under ambient conditions for thirty days after formation of each yarn. The boil-off shrinkage of each yarn was measured after storage for 30 days. The boil-off shrinkage was measured in accordance with the process set forth above defining the term “boil-off shrinkage”. The boil-off shrinkage after thirty days for each yarn is shown in Table 2 below. TABLE 2 Take-up Speed (m/min) 30 Day Boil-Off Shrinkage (%) 3500 5 4000 8 4500 5

The 30 day boil-off shrinkage results show that PTT partially oriented yarns prepared in accordance with the process of the present invention are subject to little shrinkage after aging.

EXAMPLE 3

A partially oriented PTT yarn spun with godet rolls taking up the yarn at a take-up speed of 4000 m/min was prepared in accordance with the process of the present invention, and the boil-off shrinkage of the yarn was measured from the initial formation of the yarn to thirty days from the initial formation of the yarn to determine the shrink-stability of the yarn. PTT polymer having an intrinsic viscosity of 0.92 dl/g was dried to less than 30 ppm moisture, and then was melted and extruded at 255° C. using a 50 mm diameter barrier screw extruder with a L/D ratio of 25/1 through a spinneret having 0.3 mm diameter die holes into 36 filament fibers. The fibers were quenched at a temperature of 21° C. to a yarn temperature of less than 50° C., passed through a pair of unheated godet rolls in the form of an S-wrap, and wound up with a Teijin-Sekki winder to produce an 85 denier yarn. The yarn was spun with the godet rolls taking-up the yarn at a take-up speed of 4000 m/min. Within 24 hours of preparing the yarn, the initial boil-off shrinkage of the prepared yarn was measured. The boil-off shrinkage of the yarn was measured in the same manner as described above in Example 2. The yarn was aged for 30 days under ambient conditions, and then the boil-off shrinkage of the yarn was measured again. The results are shown in Table 3 below. TABLE 3 Take-up Initial boil-off 30 day boil-off Speed (m/min) shrinkage (%) shrinkage (%) 4000 17.3 11.1

The difference between the measured initial boil-off shrinkage of the yarn and the 30 day boil-off shrinkage of the yarn is quite small at 6.2%, and indicates that the PTT partially oriented yarn prepared in accordance with the process of the invention is subject to little shrinkage upon aging.

EXAMPLE 4

Partially oriented PTT yarns were prepared in accordance with the process of the present invention at take-up speeds of 3500 m/min, 4000 m/min, and 4500 m/min and measured for tenacity and elongation-at-break. The yarns were prepared in accordance with the process set forth in Example 3, except that the yarns were taken up at take-up speeds of 3500 m/min, 4000 m/min, and 4500 m/min. Each yarn was measured for tenacity and elongation-at-break. The results are shown in Table 4 below. TABLE 4 Take-up Speed (m/min) Tenacity (g/den) Elongation at break (%) 3500 2.60 80 4000 2.93 70 4500 2.88 67

The measured tenacity and elongation at break of the yarns indicate that the PTT partially oriented yarns prepared in accordance with the invention are relatively strong.

EXAMPLE 5

A yarn package was prepared according to the process of the present invention, and the yarn package was observed over 30 days to detect any changes in shape induced in the package by yarn shrinkage. PTT having an intrinsic viscosity of 0.92 dl/g was melt spun through a 32 hole spinneret having 0.25 mm diameter die holes into a 32 filament 89 denier partially oriented yarn. The filaments were quenched with quench air having a temperature of 15° C. and a velocity of 0.35-0.45 m/sec to a yarn temperature less than 50° C. The yarn was passed through a pair of unheated godet rolls operating at a take-up speed of 4000 m/min and wound onto a yarn package. The yarn package weight with the yarn wound thereon was 8.1 kg. The yarn package was inspected for bulge and saddle back initially upon formation of the yarn package and again 30 days after formation of the yarn package. The package shape remained virtually unchanged from the initial formation of the yarn package to 30 days after formation of the yarn package, demonstrating the shrink-stability of the yarn and the yarn package.

EXAMPLE 6

For comparative purposes, a partially oriented PTT yarn was prepared by a process not in accordance with the present invention at a take-up speed of 2500 m/min and measured for crystallinity, birefringence, crystal orientation function, and heat of fusion. The yarn was prepared in accordance with the process set forth in Example 1 except that the yarn was taken up at a take-up speed of 2500 m/min. The crystallinity, birefringence, crystal orientation function, and heat of fusion of the yarn were measured. The resulting measurements are reported in Table 5 below. TABLE 5 Take-up Crystal Speed Heat of Fusion Crystallinity orientation (m/min) (cal/g) (%) Birefringence function 2500 8.1 23.2 0.043 0.40

The measured crystallinity, birefringence, crystal function, and heat of fusion for the yarn as shown in Table 5, indicate that the yarn spun and taken up at a take-up speed of 2500 m/min has significantly less orientation than PTT partially oriented yarns spun and taken up at take-up speeds of 3500 m/min or higher (as shown in Table 1).

EXAMPLE 7

For comparative purposes, the boil-off shrinkage after thirty days of a PTT yarn prepared at a take-up speed of 2500 m/min (not in accordance with the present invention) was measured to determine the shrink capacity of the yarn after aging. The yarn was prepared as disclosed in Example 6 above. The boil-off shrinkage after 30 days from the formation of the yarn was measured as described in Example 2 above. The boil-off shrinkage of the yarn after thirty days is shown in Table 6 below. TABLE 6 Take-up Speed (m/min) 30 Day Boil-Off Shrinkage (%) 2500 26

The 30 day boil-off shrinkage results of the yarn taken up at a take-up speed of 2500 m/min shows that the yarn has substantial capacity to shrink 30 days after the formation of the yarn, particularly compared to PTT partially oriented yarns prepared in accordance with the process of the present invention (as shown in Table 2).

EXAMPLE 8

For comparative purposes, a partially oriented PTT yarn was prepared by a process not in accordance with the present invention at a take-up speed of 2500 m/min and measured for tenacity and elongation-at-break. The yarn was prepared in accordance with the process set forth in Example 3 except that the yarn was taken up at a take-up speed of 2500 m/min. The yarn was measured for tenacity and elongation-at-break. The results are shown in Table 7 below. TABLE 7 Tenacity Elongation at break Take-up Speed (m/min) (g/den) (%) 2500 2.25 90

The measured tenacity of the yarn indicates that the yarn taken up at a take-up speed of 2500 m/min is relatively weak compared to yarns spun in accordance with the process of the present invention (as shown in Table 4). 

1. A yarn comprising, a poly (trimethylene terephthalate) yarn having a crystal orientation function of at least about 0.6 and an elongation at break of between 65% and 110%.
 2. The yarn of claim 1 wherein the poly (trimethylene terephthalate) yarn has a heat of fusion of at least about 12 calories/gram.
 3. The yarn of claim 1 wherein the poly(trimethylene terephthalate) yarn has an initial birefringence of at least about 0.05.
 4. The yarn of claim 1 wherein the poly(trimethylene terephthalate) yarn has an initial boil-off shrinkage of at most about 22%.
 5. The yarn of claim 1 wherein the poly(trimethylene terephthalate) yarn has a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less about 10% to the initial boil-off shrinkage.
 6. The yarn of claim 1 wherein the poly(trimethylene terephthalate) yarn has a meridianal two-point small-angle X-ray scattering pattern corresponding to a crystalline/amorphous phase lamellar periodicity of from about 50 to about 100 angstroms.
 7. The yarn of claim 1 wherein the poly(trimethylene terephthalate) yarn has a tenacity of at least 2.5 g/denier.
 8. A yarn package comprising the yarn of claim
 1. 9. The yarn package of claim 8, wherein the yarn package weighs at least about 5 kg.
 10. A process for forming a poly(trimethylene terephthalate) yarn comprising: melt-spinning poly(trimethylene terephthalate); cooling the melt-spun poly(trimethylene terephthalate) into a multi-filament yarn having a yarn temperature less than 50° C.; and taking up the multi-filament yarn having a yarn temperature less than 50° C. at a take-up speed of at least about 3500 m/min while maintaining the yarn at a yarn temperature of less than 50° C.
 11. The process of claim 10 further comprising winding the yarn onto a yarn package.
 12. The process of claim 11 further comprising: unwinding the yarn from the yarn package; and drawing and texturing the unwound yarn.
 13. The process of claim 12 wherein the yarn is unwound from the yarn package at least one day after winding the yarn onto the yarn package.
 14. A yarn comprising, a polytrimethylene (terephthalate) yarn having an initial boil-off shrinkage of at most 22%; a boil-off shrinkage after thirty days of from the initial boil-off shrinkage less 10% to the initial boil-off shrinkage; and an elongation at break of between 65% and 110%.
 15. The yarn of claim 14 wherein the poly (trimethylene terephthalate) yarn has a heat of fusion of at least 12 calories/g.
 16. The yarn of claim 14 wherein the poly (trimethylene terephthalate) yarn has a tenacity of at least 2.5 g/denier.
 17. A yarn package comprising the yarn of claim
 14. 